This invention relates to electrosurgical instruments, and more particularly to an alarm system for such instruments which provides for instant alerting of the surgeon of the presence of a dangerous situation in the electrical system of the device being used. More particularly, this invention relates to a disposable electrosurgical instrument having incorporated into the surface thereof a warning light which is incorporated into the circuitry leading to the electrode forming the blade or other cutting active portion of the instrument.
The arrangement is such that the light is in the direct vision of the surgeon during his surgical procedures so that any variation in the circuitry, such as an unwanted surge of electrical current, is immediately made apparent to the surgeon by the sudden brilliant lighting of the warning lamp of the invention.
In electrosurgery, an electrical current flows through a circuit that begins at a high-frequency oscillator within an electrosurgical unit, goes through an active cable to an active electrode forming the blade of the unit to the patient, and then returns from the patient by way of a dispersive electrode and a cable to the electrosurgical unit. The dispersive electrode has a relatively large contact area to prevent burns to the patient's body.
By contrast, the relatively small contact area between the tissue and the active electrode tip causes a concentration of current (high current density) that heats the tissue at this point, thus allowing for the "electrosurgical" cutting of tissue. However, because of the concentration of current at the cutting point, it is important to have an immediate response when that concentration increases beyond a desired level because of some failure in the electric circuit.
With this invention, provision is made for continuous monitoring of the surgical procedure with the indicator being held in the surgeon's hand so that immediate action may be taken if sudden change occurs in the electronic circuit. This is done without the surgeon having to observe a surgical generator panel, without having to listen for an audio alarm of some kind from the panel or without having to wait for a nurse's observation of the generator's output to correct improper settings.
Thus, with the invention herein, the blade, or other cutting instrument, is the output electrode and it is connected to a surgical generator which is the input source of the device. The active return of the generator is connected to the patient during the electrosurgical procedure. During this procedure, in accordance with the invention herein, a parallel lamp mounted directly upon the disposable handle of the electrical surgical knife unit and a resistor therefor in combination become a passive component for the high frequency current of the generator. Because of this, all current passes through the lamp and the resistor network during operation procedures. Thus, any variation in the current output is immediately disclosed in the lamp, and immediately alerts the surgeon directly in his line of vision so that the blade is immediately removed from the surgical site.
In considering generally the conditions for operation of the invention herein, it should be noted that in operation the lamp's filament resistance is non-linear, and changes from a very low resistance when cold to a relatively high resistance when hot. Thus, in accordance with this invention, a lamp is selected with a sharp change in resistance as current is increased so that the light "turn-on" point is at a chosen current level. Moreover, a proper choice of parallel resistor to operate in combination with the lamp is selected. Typically, the light output is measured at 0.2 amps increments of current. With this arrangement, at 0.4 amps, light output is nearly non-measurable. By contrast, at 0.8 amps, a brilliant source of light is obtained.
Other objects and advantages of this invention will be apparent from the following description, the accompanying drawings, and the appended claims.